1. Field of the Invention
The present invention relates to tone parameter control apparatus used in electronic musical instruments or the like which control tone parameters used to generate a musical sound.
2. Description of the Related Art
Conventionally, it is well known that the amplitude and frequency of a musical sound generated from an electronic instrument or the like are changed in response to the output of a low frequency oscillator (LFO) or an envelope oscillator to apply various musical effects to the generated musical sound.
However, the output from such LFO or envelope oscillator is very monotonous, so that the effects produced by the use of such outputs are artificial and unnatural.
In view of such situation, it has been considered to modulate tone parameters required for generation of a musical sound with a more irregular natural signal, for example, of noise having a power spectrum of a magnitude of 1/f inversely proportional to a frequency of f, or a 1/f sway (or fluctuation) signal and not a signal from such LFO or envelope oscillator.
By the use of this system, addition of sway (or fluctuation) of a natural tone which is not provided by the conventional musical sound generator is realized.
However, easy addition of this sway (or fluctuation) may cause the following problems. Throughout the following description and claims, the term sway signal is used, which is synonymous with the term fluctuation signal.
If a 1/f sway signal is separately applied to tone parameters without considering the relationship between the tone parameters, for example, when a plurality of tones are generated in unison, a natural sway effect of a tone based on the 1/f sway signal would undesirably be canceled greatly and reduced.
If 1/f sway signals are added to several tone parameters of the same kind, for example, on the modulation depth of the LFO applied separately to three different tone ranges of an electronic instrument and if a musical sound in one tone range and then another musical sound in another range are generated sequentially, the sway levels of the tones may undesirably differ from each other and the tone would sound unnatural.